Sensor system incorporated into a motor vehicle for detecting the presence of an emergency vehicle's sounding siren are known in the art. The prior attempts to provide warning signals as known in the prior art have taken two forms of methods and apparatus. In one form of warning system both the emergency vehicle and non-emergency vehicle are equipped with a special transmitter and receiver, respectively, to activate an alarm system. Such systems include apparatus for deactivating the motor vehicle radio's speakers in response to the reception of a signal from the emergency vehicle transmitter. Prior art of this type of sensing system are typified by U.S. Pat. Nos. 4,794,394; 4,238,778 and German patent 29 31 977.
The second type of sensor systems incorporate the sensing system in a motor vehicle detecting the siren sounds emitted by an approaching emergency vehicle. These prior art systems include visual and/or audible alarms that are activated when the emergency vehicle having its siren operative reaches a predetermined proximity to the motor vehicle in which the siren sensor is mounted. Patents of this type are U.S. Pat. Nos. 4,785,474; 4,587,522; 4,158,190 and 3,859,623.
The problem of a motor vehicle operator hearing an approaching emergency vehicle's siren still persists despite the aforementioned attempts to solve the problem and to our knowledge no known sensing systems are presently commercially available. The problem, however, still persists since the environmental noises continue to increase and motor vehicles, passenger vehicles and trucks or the like, are constructed so that the closed windows tend to seal off the environmental noises but yet the motor vehicles contain other devices that impair a motor vehicle operator's hearing such as radios with a multiplicity of speakers, tape players and/or compact disc players, air conditioning and/or heating equipment. Obviously, the problem is aggravated when the windows of the motor vehicle are open and the aforementioned accessories are in use.
The inability of a motor vehicle operator to hear an approaching emergency vehicle's sirens has resulted in accidents, particularly at intersections, that result in Collisions with the emergency vehicles and with the consequential damages to the vehicles, property, personal injuries and even death as well as the inability of the emergency vehicle to arrive at the place of the emergency. The problems of prior art known systems appears to be in the complexity of the apparatus and therefore rendering the apparatus expensive to implement on a commercial basis. This includes the fact that the detection techniques of some of these prior art devices are narrowly defined for certain types of sirens and/or signals to be sensed. To a large extent, the known prior art devices are designed with the microphones sensing the siren sounds on the outside of the motor vehicle which subjects the microphone to all environmental noises found in present day traffic conditions and wind noises that may mask the siren sounds or impair operation of the sensing systems for practical uses. There is then, a present need for a method and apparatus for detecting the siren sounds of an emergency vehicle for warning motor vehicle operators of the approaching emergency vehicles in sufficient time for the motorist to take the necessary action to avoid any possible collision with the emergency vehicle and a method and apparatus that is relatively inexpensive and dependable in operation for this purpose by avoiding the problems of prior art systems.